There has been known an oil separator that separates, from the processing-target gas, mist oil contained in processing-target gas (see PTL 1, for example). The following describes this oil separator of PTL 1. Here, reference numerals described in PTL 1 are shown with parentheses.
An upper housing (2) of a cylindrical shape is provided above a lower casing of a cylindrical shape. The hollow of the upper housing (2) is closed from above by a ceiling (3), and the hollow of the upper housing (2) is closed from below by a partition (5). Inside the upper housing (2), a gas cleaning device (13) for cleaning gas is disposed, and inside the lower casing (1), a centrifugal rotor (11) for cleaning liquid is disposed.
The gas cleaning device (13) is a centrifugal oil separator, and the rotor of the gas cleaning device (13) is composed of a plurality of stacked separation disks (37). These separation disks (37) are interposed between a plate-like upper holder (36) and a lower holder (35) so that the separation disks (37) are held by these holders (35, 36). The separation disks (37), the upper holder (36) and the lower holder (35) rotate together with the centrifugal rotor (11) using hydraulic pressure of the centrifugal rotor (11). There is an opening formed at the center of each separation disk (37). The openings of the separation disks (37) are stacked vertically, forming an inlet chamber (39) at the center of the stack of the separation disks (37). The lower holder (35) has a hole (38) formed above the opening (8) of the partition (5).
Blow-by gas (processing-target gas) from a crankcase is flowing from the lower casing (1) through the opening (8) of the partition (5) and the hole (38) of the lower holder (35) into the inlet chamber (39). While the blow-by gas is flowing radially outward in clearances between the separation disks (37), mist oil contained in blow-by gas is captured by the clearances between the separation disks (37). Blow-by gas blown out from the outer edge of the separation disks (37) moves upward in the upper housing (2) and is discharged. Oil captured by the clearances between the separation disks (37) is blown toward the inner peripheral surface of the upper housing (2) due to the centrifugal force of the separation disks (37). Oil attached to the inner peripheral surface flows down along the inner peripheral surface. Thus, the processing-target gas and the mist oil contained in the processing-target gas are separated and purified.